Bone conduction speaker

Abstract

A bone conduction speaker is provided that, while it is a bone conduction speaker, additionally has a structure allowing a respiratory tract sound to be generated, thereby the high frequency characteristics thereof being improved. In the case where it is used by a hearing non-impaired person, communications at a good voice level can be made as well as in the case where it is used by a hearing impaired person. Further, when the hearing non-impaired person uses it to listen to a music, the music can be enjoyed with a high sound quality.

The invention claimed is: 
     
       1. A bone conduction speaker comprising:
 a bone conduction speaker unit in a housing thereof, the bone conduction speaker unit comprising a voice coil disposed so as to surround a center pole provided in a central portion of a yoke; 
 a pair of bar magnets fixed to opposite sides of the voice coil; 
 a first diaphragm disposed so as to cover the voice coil and the pair of bar-like magnets, the first diaphragm being fixed to an inner surface of the housing, thereby a force of inertia generated by vibration of the yoke causing the housing to be vibrated; 
 a second diaphragm, the second diaphragm being fixed to a bottom face of the bone conduction speaker unit, a peripheral part of the second diaphragm being fixed to the inner surface of the housing over an entire periphery of the peripheral part, thereby an upper air chamber being formed on an upper side of the second diaphragm, and a lower air chamber being formed on a lower side thereof; and 
 a sound emitting port being formed in a side face or a bottom face of the lower air chamber. 
 
     
     
       2. The bone conduction speaker according to  claim 1 , wherein the second diaphragm has an annular groove and/or an annular convex part in the peripheral part. 
     
     
       3. The bone conduction speaker according to  claim 1 , wherein in the central part of the second diaphragm, there is formed a circular base part for securing a gap with respect to the bottom face of the bone conduction speaker unit, the circular base part being fixed to the bottom face of the bone conduction speaker unit. 
     
     
       4. The bone conduction speaker according to  claim 1 , wherein in the central part of the second diaphragm, a weight for improving the frequency characteristics is fixedly attached to the central part of the second diaphragm, the weight securing a gap between the second diaphragm and the bottom face of the bone conduction speaker unit. 
     
     
       5. The bone conduction speaker according to  claim 1 , wherein the bottom face of the bone conduction speaker unit is provided with a convex part, the convex part securing a gap between the second diaphragm and the bottom face of the bone conduction speaker unit. 
     
     
       6. The bone conduction speaker according to  claim 1 , wherein the sound emitting port is made capable of being opened and closed. 
     
     
       7. The bone conduction speaker according to  claim 1 , wherein the housing has a low cylindrical shape, the sound emitting port being formed in a peripheral side face or a bottom face of the housing. 
     
     
       8. The bone conduction speaker according to  claim 1 , wherein the housing has a cylindrical shape at least one end of which is provided with a spherical surface, the sound emitting port being formed in the spherical surface. 
     
     
       9. The bone conduction speaker according to  claim 7 , wherein the sound emitting port is provided with a sound conduction tube that is formed, being bent so as to be directed to the inside of an ear hole in service. 
     
     
       10. The bone conduction speaker according to  claim 9 , wherein the sound conduction tube is molded integrally with the housing. 
     
     
       11. The bone conduction speaker according to  claim 9 , wherein the sound conduction tube is molded separately from the housing, and posteriorly attached to the sound emitting port.